Protein-coding circular RNA enhances antiviral immunity via JAK/STAT pathway in Drosophila.

RNA interference (RNAi) drives powerful antiviral immunity in plants and animals so that many viruses must express viral suppressor of RNAi (VSR) to establish virulent infection. However, little is known about the immune responses conferring resistance against viruses that have evolved the counter-defensive strategy to suppress antiviral RNAi. In this study, we discover that Drosophila cells infected with Drosophila C virus (DCV), a natural viral pathogen of Drosophila known to harbor a potent VSR, exhibit heightened expression of circular RNA circZfh1. circZfh1 confers virus resistance in the presence of viral suppression of antiviral RNAi. Furthermore, we validate that circZfh1 encodes a 274-amino acid protein, CRAV, essential for its antiviral activity. Notably, CRAV differs from its parental Zfh1 gene in a different reading frame, with the C-terminal 69 amino acids unique to CRAV. Our analysis also reveals the presence of CRAV in species within the melanogaster subgroup, with the C-terminal unique fragment undergoing accelerated evolution. Expression of CRAV upregulates the expression of the cytokine Upd3, which binds to its receptor, stimulating the JAK-STAT pathway and enhancing the immune response to DCV infection. Notably, CRISPR/Cas9 knockout of circZfh1 significantly enhances DCV replication in vitro and in vivo, with circZfh1-knockout adult flies displaying heightened disease susceptibility to DCV. In summary, our findings unveil a Drosophila protein-coding circular RNA that activates an innate immune signaling pathway crucial for virus resistance following the suppression of antiviral RNAi by viruses, thereby elucidating a novel counter-defensive strategy.IMPORTANCEEukaryotic hosts possess a complex, multilayered immune system that guards against pathogen invasion. In fruit flies, RNA interference (RNAi) drives robust antiviral immunity, prompting many viruses to express viral suppressors of RNAi (VSRs) to establish virulent infections. However, little is known about immune responses that confer resistance against viruses with potent VSRs. In this study, we discovered that Drosophila cells infected with Drosophila C virus (DCV), a natural viral pathogen possessing a potent VSR, upregulated the expression of circular RNA circZfh1. circZfh1 exhibits DCV-specific antiviral activity, encoding a 274-amino acid protein, CRAV, crucial for its antiviral effects. As a different reading frame from its parental Zfh1 gene, the C-terminal 69 amino acids are unique to CRAV, undergoing faster evolution. CRAV activates the JAK-STAT pathway, enhancing the immune response to DCV infection. Therefore, our work uncovers a new strategy for suppressing viral counter-defense through protein-coding circular RNA in fruit flies.

Regulation of ubiquitination and antiviral activity of Cactin by deubiquitinase Usp14 in Drosophila.

Cactin, a highly conserved protein, plays a crucial role in various physiological processes in eukaryotes, including innate immunity. Recently, the function of Cactin in the innate immunity of Drosophila has been explored, revealing that Cactin regulates a non-canonical signaling pathway associated with the Toll and Imd pathways via the Cactin-Deaf1 axis. In addition, Cactin exhibits specific antiviral activity against the Drosophila C virus (DCV) in Drosophila, with an unknown mechanism. During DCV infection, it has been confirmed that the protein level and antiviral activity of Cactin are regulated by ubiquitination. However, the precise ubiquitination and deubiquitination mechanisms of Cactin in Drosophila remain unexplored. In this study, we identified ubiquitin-specific protease 14 (Usp14) as a major deubiquitinase for Cactin through comprehensive deubiquitinase screening. Our results demonstrate that Usp14 interacts with the C_Cactus domain of Cactin via its USP domain. Usp14 efficiently removes K48- and K63-linked polyubiquitin chains from Cactin, thereby preventing its degradation through the ubiquitin-proteasome pathway. Usp14 significantly inhibits DCV replication in Drosophila cells by stabilizing Cactin. Moreover, Usp14-deficient fruit flies exhibit increased susceptibility to DCV infection compared to wild-type flies. Collectively, our findings reveal the regulation of ubiquitination and antiviral activity of Cactin by the deubiquitinase Usp14, providing valuable insights into the modulation of Cactin-mediated antiviral activity in Drosophila.IMPORTANCEViral infections pose a severe threat to human health, marked by high pathogenicity and mortality rates. Innate antiviral pathways, such as Toll, Imd, and JAK-STAT, are generally conserved across insects and mammals. Recently, the multi-functionality of Cactin in innate immunity has been identified in Drosophila. In addition to regulating a non-canonical signaling pathway through the Cactin-Deaf1 axis, Cactin exhibits specialized antiviral activity against the Drosophila C virus (DCV) with an unknown mechanism. A previous study emphasized the significance of the Cactin level, regulated by the ubiquitin-proteasome pathway, in modulating antiviral signaling. However, the regulatory mechanisms governing Cactin remain unexplored. In this study, we demonstrate that Usp14 stabilizes Cactin by preventing its ubiquitination and subsequent degradation. Furthermore, Usp14 plays a crucial role in regulating the antiviral function mediated by Cactin. Therefore, our findings elucidate the regulatory mechanism of Cactin in Drosophila, offering a potential target for the prevention and treatment of viral infections.

Regulation of phase separation and antiviral activity of Cactin by glycolytic enzyme PGK via phosphorylation in Drosophila.

Liquid-liquid phase separation (LLPS) plays a crucial role in various biological processes in eukaryotic organisms, including immune responses in mammals. However, the specific function of LLPS in immune responses in Drosophila melanogaster remains poorly understood. Cactin, a highly conserved protein in eukaryotes, is involved in a non-canonical signaling pathway associated with Nuclear factor-κB (NF-κB)-related pathways in Drosophila. In this study, we investigated the role of Cactin in LLPS and its implications for immune response modulation. We discovered that Cactin undergoes LLPS, forming droplet-like particles, primarily mediated by its intrinsically disordered region (IDR). Utilizing immunoprecipitation and mass spectrometry analysis, we identified two phosphorylation sites at serine residues 99 and 104 within the IDR1 domain of Cactin. Co-immunoprecipitation and mass spectrometry further revealed phosphoglycerate kinase (PGK) as a Cactin-interacting protein responsible for regulating its phosphorylation. Phosphorylation of Cactin by PGK induced a transition from stable aggregates to dynamic liquid droplets, enhancing its ability to interact with other components in the cellular environment. Overexpression of PGK inhibited Drosophila C virus (DCV) replication, while PGK knockdown increased replication. DCV infection also increased Cactin phosphorylation. We also found that phosphorylation enhances the antiviral ability of Cactin by promoting liquid-phase droplet formation. These findings demonstrate the role of Cactin-phase separation in regulating DCV replication and highlight the modulation of its antiviral function through phosphorylation, providing insights into the interplay between LLPS and antiviral defense mechanisms. IMPORTANCE: Liquid-liquid phase separation (LLPS) plays an integral role in various biological processes in eukaryotic organisms. Although several studies have highlighted its crucial role in modulating immune responses in mammals, its function in immune responses in Drosophila melanogaster remains poorly understood. Our study investigated the role of Cactin in LLPS and its implications for immune response modulation. We identified that phosphoglycerate kinase (PGK), an essential enzyme in the glycolytic pathway, phosphorylates Cactin, facilitating its transition from a relatively stable aggregated state to a more dynamic liquid droplet phase during the phase separation process. This transformation allows Cactin to rapidly interact with other cellular components, enhancing its antiviral properties and ultimately inhibiting virus replication. These findings expand our understanding of the role of LLPS in the antiviral defense mechanism, shedding light on the intricate mechanisms underlying immune responses in D. melanogaster.

Profiling the Tumor-Infiltrating Lymphocytes in Gastric Cancer Reveals Its Implication in the Prognosis.

Gastric cancer is the fifth most common malignancy and the third leading cause of cancer-related mortality worldwide. Immunotherapy offers promising new treatment options for gastric cancer patients; however, it is only effective in a limited fraction of patients. In this study, we evaluated the composition of 22 tumor-infiltrating lymphocytes (TILs) in TCGA Stomach Adenocarcinoma (STAD) using deconvolution-based method by analyzing the publicly available bulk tumor RNA-seq data. The patients were classified into high-TIL and low-TIL subtypes based on their immune cell profiles and prognosis outputs. The differentially expressed genes (DEGs) between the two subtypes were identified, and GO/KEGG analysis showed that broad immune genes, such as PD-L1 and PD-1, were highly expressed in the high-TIL subtype. A comprehensive protein-protein interaction (PPI) network centered on DEGs was built, and 16 hub genes of the network were further identified. Based on the hub genes, an elastic model with 11 gene signatures (NKG7, GZMB, IL2RB, CCL5, CD8A, IDO1, MYH1, GNLY, CXCL11, GBP5 and PRF1) was developed to predict the high-TIL subtype. In summary, our findings showed that the compositions of TILs within the tumor immune microenvironment of stomach cancer patients are highly heterogeneous, and the profiles of TILs have the potential to be predictive markers of patients' responses and overall survival outcomes.

Integrated analysis of whole genome and transcriptome sequencing in a young patient with gastric cancer provides insights for precision therapy.

Gastric cancer is a leading cause of cancer-associated deaths worldwide and is considered to be an age-related disease. In younger patients, gastric cancer is biologically more aggressive, and prognosis is worse compared with that in elderly patients. In the present case report, the whole genome and transcriptome was sequenced in a 26-year-old patient with gastric cancer who presented with gastric cancer-related symptoms and was admitted to the First Affiliated Anhui Medical Hospital (Hefei, China) in December 2016. In total, 9 germline and 4 somatic mutations were identified in the patient, and there were more deleterious sites in the germline mutated genes. Genes with somatic mutations, such as MUC2, MUC4, SLC8A2, and with structural variations, including CCND3, FGFR2 and FGFR3, were found to be differentially expressed. Cancer-associated pathways, such as the 'calcium signaling pathway', 'cGMP-PKG signaling pathway' and 'transcriptional mis-regulation' were also enriched at both the genomic and transcriptomic levels. The genes found to have germline (SFRP4), somatic (MUC2, MUC4, SLC8A2) mutations, or structural variations (CCND3, FGFR2 and FGFR3) were differentially expressed in the patient and could be promising precision therapy targets.

Exploration of the genomic landscape of a long-term surviving stage III colorectal cancer patient identifies recurrent and rare mutations: a case report.

A 40-year old female patient from the Chinese Han population presented colorectal cancer (CRC) related symptoms including abdominal discomfort, tenesmus and severe back pain, and was admitted to the First Affiliated Anhui Medical University in October, 2008. The size of her tumor was 3 cm × 3 cm, and the carcinoma had invaded the serosa layer, covering 3/4 of the intestine tube. She was diagnosed with stage III CRC after examination. The patient presented a good prognosis with over 8-year survival after curative surgery and adjuvant therapy with Oxaliplatin and Huaier granules, a traditional Chinese medicine. Using the whole-genome sequencing (WGS) data, we profiled the germline and somatic mutations and obtained an all-inclusive data of the genomic alterations. The genomic alterations were compared with those of stage III CRC patients in The Cancer Genome Atlas Network (TCGA). Mutations in APC, TP53, KRAS, SMAD4, FBXW7 and PIK3CA defined as drivers in TCGA patients were not recorded in our study. However, mutations in MUC4, MUC16, ARID1B, BAZ1A, BRCA2, CTNND1 and NCOA2 rarely reported in TCGA patients were predominant in our patient. Additionally, we observed loss of heterozygosity (LOH) in POLE, RET, BMPR1A, NCOA4 and 30 other genes in contrast to deletion and amplification events recorded in TCGA patients. Overall, we produced a genomic mutation profile of a long-term surviving CRC patient and identified recurrent and rare mutations that could provide a valuable resource for further study into the alterations that characterize advanced CRC which may be useful to design clinical therapy for personalized medicine.

Complete genome sequence of a novel velarivirus infecting areca palm in China.

The complete genome of a novel virus, provisionally named areca palm velarivirus 1 (APV1), was identified in areca palm exhibiting leaf yellowing symptoms in Hainan province, China. The genome of APV1 consists of 16,080 nucleotides and possesses 11 open reading frames (ORFs), sharing 56.4% nucleotide sequence identity with little cherry virus 1 (NC_001836.1). The genome organization of APV1 is highly similar to that of members of the genus Velarivirus (family Closteroviridae). Phylogenetic analysis placed APV1 together with members of the genus Velarivirus.